How does Extra Rage ("you can rage for 6 additional rounds per day") affect Raging Blood ("You can enter this lesser bloodrage twice per day, for up to 4 rounds")?
At least in Hero Lab, having Raging Blood opens up Extra Rage as a valid feat, but it doesn't show any adjustment to the bloodrage uses or tracking. Does it become twice per day for up to 10 rounds or twice per day for 7 rounds each? It seems to depend on whether Raging Blood is interpreted as a max of 4 rounds per day with 2 uses per day, or 2 uses per day with 4 rounds per use. Raging Blood tracking in Hero Lab simply shows 2 boxes, which seems to indicate 2 uses at 4 rounds each. Still, I'm confused!
Ask your GM.
The most conservative answer is it's 4 rounds per day total for Raging Blood, and you can enter a rage twice per day to use those available rounds.
Extra Rage would add a total of 6 rounds, that you could expend, giving a total of 10 rounds of rage. This is the most straight forward interpretation of the rules.
The other possibility would be you have two rages which can each be up to 4 rounds. And you can use the pool of 6 rounds on either rage, but don't need to split them evenly between them.